The invention relates to an acoustic building structure which is intended to be fixed to the framework of the building and which comprises at least one acoustic assembly comprising a panel of mineral wool and a bearer of the said panel of mineral wool.
Acoustic insulation of a building is commonly obtained using structures of the mass-spring-mass type, an example of which is given in document EP 0921242. Such a structure is made up of two masses each of which consists of a rigid element and which are separated by a panel of mineral wool, such as glass wool, associated with an air gap to form the spring. The two rigid elements are placed one on each side of the framework of the building and fixed mechanically to this very framework or to metal rails added to the framework. These elements consist of sheet metal trays of U-shaped cross section which are lined, inside the U, with a panel of mineral wool, such as rock wool, to improve the mass effect.
The structure described in that document advantageously allows the rigid elements to be fixed directly to the framework of the building or to metal rails associated with the framework without the need for intermediate fixing means. However, the structure, because of the sheet metal nature and tray-shape of the rigid elements, also reaches a cost that it would be desirable to reduce.
Moreover, apart from being related to the nature of the walls, the performance of the acoustic insulation of the building is related to the thickness and to the nature of the spring and of the damper, and to the mass per unit area of the structure which is given by the amount of mineral wool inserted into the bearer and by the sheet metal nature of the bearer. Nonetheless, the mass per unit area is sometimes insufficient and it is therefore necessary, in order to improve the acoustic performance, to add an additional filler into the bottom of the tray, for example a sheet of plasterboard, thus further increasing the cost price of the structure.
The object of the invention is therefore to provide an acoustic structure, particularly one which is of the mass-spring-mass type, which while retaining the advantages of high-performance acoustic insulation and simplicity in the way in which it is fixed to the framework of the building, has a lower overall cost.
According to the invention, the acoustic structure is characterized in that the bearer consists of a pair of one lower and one upper section pieces spaced apart by a spacing p and each of which comprises a respective web, each facing the other, and a respective flange bent at right angles to the associated web, the flanges being in one and the same plane and facing towards each other, and the panel of mineral wool being housed between the webs of the section pieces, and the acoustic assembly includes a rigid panel fixed against the outer faces of the flanges of the section pieces.
This structure has the advantage that the acoustic insulation can directly obtain sufficient mass per unit area without the need to add other thicknesses of surfacing elements as is generally the case with the sheet metal trays of the prior art, which have additional plasterboard sheets placed in the bottom of them.
According to a first embodiment of the section pieces, the upper section piece comprises, on the other side of the web, parallel to and in the opposite direction to the flange, a second flange intended for attaching the acoustic assembly against the framework of the building.
Advantageously, the lower section piece and the upper section piece in this embodiment have complementary shapes so that the upper section piece of the said assembly collaborates with the lower section piece of a second acoustic assembly intended to be assembled with the said first acoustic assembly.
According to a second embodiment of the section pieces, the lower section piece and upper section piece are identical and each has, parallel to the flange, an additional flange so that it has a U-shaped section such that the openings of the U face one another and between which the panel of mineral wool is trapped, the acoustic assembly being fixed to the framework of the building using at least two fixing pieces between which the section pieces are intended to be held, and at least one of which is intended to be fixed to the framework.